Automatic choke for outboard motors



May 8, 1962 v w. B. BURKETT 3,033,185

AUTOMATIC CHOKE FOR OUTBOARD MOTORS Filed Nov. 16, 1959 2 Sheets-Sheet 1INVENTOR. Ml Fokb R Bl/RKFI'? I Jrramwms y 1952 w. B. BURKETT 3,033,185

AUTOMATIC CHOKE FOR OUTBOARD MOTORS Filed Nov. 16, 1959 2 Sheets-Sheet 2.FIE'. 4

INVENTOR. Ma -cap B. Bl/RAETT lrroxmsm This invention relates generallyto outboard motors and more specifically to an outboard motor having afully progressive automatic choke with a coolant system operated chokeunloader.

Previous automatic chokes often included an induction manifold vacuumoperated piston to unload the choke during engine warmup periods forpreventing flooding the carburetor and subsequently stopping the engine.Manifold vacuum, while somewhat related to engine speed, is not directlyindicative thereof and thus the engine may be choked differently at oneengine speed.

This invention provides an automatic choke in an outboard motor in whichduring warmup the engine choke unloading is proportioned to true enginespeed or r.p.m. A closed water pressure line is connected between apressure responsive choke unloading diaphragm and the engine coolingsystem having water or coolant pressures related to true engine speed.The coolant pressure overrides a calibrated spring yieldably urging toflex the diaphragm which is suitably limited in flexing for determin ingthe maximum the choke may be unloaded. A thermal bimetallic motor isalso connected to the choke valve for opening same as the enginetemperature approaches normal. ince the pressure diaphragm provides onlylimited choke valve opening, the motor disengages the valve from thediaphragm as the engine temperature nears normal operating temperature.

With a fast idle attachment on the carburetor, the spring load diaphragmmay be utilized to determine and adjust the maximum fast idle speeddirectly from actual engine speed.

Accordingly it is an object of the present invention to provide anautomatic choke on an outboard motor having an engine warmup controlresponsive to engine speed to unload the choke in a predeterminedproportion to engine speed.

It is another object of this invention to provide an engine speedcontrolled fast idle attachment to an automatic choke in an outboardmotor.

These and other more detailed and specific objects will be disclosed inthe course of the following specification, reference being had to theaccompanying drawings, in which- FIG. 1 is a side elevational view of anoutboard motor unit embodying the present invention.

P16. 2 is a vertical sectional and enlarged view taken along line 2-2 inFIG. 1.

FIG. 3 is an enlarged vertical sectional view of an exemplary thermostatspring motor as taken along line 33 in FIG. 2.

FIG. 3A is an enlarged horizontal sectional view of an exhaust stovesection for use with the present invention as viewed looking down fromthe FIG. 1 engine.

FIG. 4 shows an exemplary coolant pressure responsive unit in anenlarged vertical sectional View taken along line 44 of FIG. 2.

FIG. 5 is a perspective view of an exemplary fast idle linkage for usein the present invention.

With more particular reference now to the drawings like numbers denotelike parts and structure features in the various views. An outboardmotor has an internal combustion engine with the usual intake orinduction manifold 12 having a carburetor 14 mounted thereon and beingin communicative relation therewith. An air in take assembly 16 forcleaning the combustion air before entering the carburetor is provided,the details of which are unimportant to this invention. 18 is rotatablymounted through opposing sides of carburetor 14 in a rotatable sleeve 21which eccentrically mounts a choke valve 20. A spring linkage 211Ayieldably urges the sleeve 21 and thus the valve 20 to rotate with theshaft 18. The valve 20 is rotatable between a closed position in whichthe valve is perpendicular to the air intake passageway 22 axis and anopen position in which the valve is parallel to the axis.

The position of choke valve 20 is controlled through spring linkage 21Aby the thermal bimetallic motor 24, coolant pressure responsivediaphragm unit 26 and a spring 28. The spring 28 is fixedly attached atone end to the carburetor 14, such as by a screw, and the otherend beinginserted into a slot 28A in the shaft 18 while under tension for urgingthe shaft 18 to close valve 20.

When initially starting the outboard motor engine the bimetallic springmotor 24 and the spring 28 completely close the choke valve 20. When theengine is started the air drawn through the passageway 22 tends tooverride the biasing of spring linkage 21A to allow limited opening ofthe choke valve. As the engine fires, more air is required to sustaincombustion requiring that valve 2% be further opened. As the enginebegins to operate the coolant system 36' rotary impeller engine shaftdriven pump 30A provides water under pressure from outside the outboardmotor unit. The cooling system fluid circuit further includes engineintake tube 303, engine water jacket 30D and discharge tube 300 forreturning the water to outside the unit. Water under pressure isprovided from jacket 30D through closed tube 32 to the unit 26. The unit26 responds to the coolant or water pressure by the flexure diaphragm 34against the calibrated spring 36 to move the L-shaped rod 38 againstnonrotatably mounted choke valve lever 40 to tend to open valve 2t inproportion to engine speed. The spring 28, in addition to urging thevalve 20 toward the closed position, also urges the lever 40 against thetransversely bent end, 38A, of rod 38, thereby removing lost motiontherebetween.

Pressure unit 26 preferably has a diaphragm travel limiting stop bearing42 which axially slidably supports the rod 38 and limits the diaphragmflexing, and thus the valve opening, by its inner end engaging thediaphragmrod connection as at 44. The bearing 42 is screwed intoretaining bushing 46 which in turn is screwed into the unit 26 housing.Alternately the rod 38 may be slida'bly supported in the unit 26 housingwith the diaphragm flexing limiting and the spring retaining beingaccomplished by housing itself.

While the pressure unit 26 may be constructed to fully open the valve 20at a predetermined engine speed, it is preferred that the thermalbimetallic spring motor 24 be utilized to keep the valve 20 completelyopen after the engine is at normal operating temperature. The motor 24consists of a spiral bimetallic thermostat spring 48 fixedly attached atits radially outer end to stationary mounting member 50. Fresh air isdrawn by manifold 12 vacuum through the air inlet tube 52 which includesa heater section 52A extending through the engine exhaust housing 54 forheating the air in proportion to the engine operating temperature. Theair passes over the spring 48 heating it in proportion to the engineexhaust temperature, thence through the tube 56 into the inductionmanifold 12. As the spring 48 is heated the bimetallic thermostaticaction causes the spring tension to relax, moving the inner endoutwardly and to the right as viewed in FIG. 3. The inner end of spring48 is pivotally connected, by connecting means 60, to choke Patented May8, 1962 A choke valve shaft operating rod 58 which in turn is connectedto choke lever 62 on shaft 18 for opening and closing valve 20 inproportion to engine temperature.

As illustrated, the motor 24 is operative to fully open the valve 28,thereby freeing the lever 46 from the pressure unit linking choke rodend 33A to make the unit 26 ineffective for operating the choke. Duringwarmup at high engine speeds pressure unit 26, in opening the valveoverrides the urging of spring 28 and motor 24. Either pressure unit 26or the motor 24 may open the valve 20. When the diaphragm 34- flexing islimited to partially open the valve 20, although not necessary, it ishighly desirable that linkage to the lever 40 be made unidirectionallyoperative, as shown, permitting the motor 24 to independently open thevalve for etficient engine operation at normal operating temperatures.Purther, with the diaphragm being limited in flexing the spring tensionof the motor element 48, the spring 28 and pressure unit 26 may becalibrated together and the spring 36 eliminated; the calibrated biasagainst the diaphragm 34 then being transmitted through the choke valvelinkages.

As aforementioned, a fast idle is preferred when an automatic choke isprovided. Particularly referring now to FIG. it is seen that choke lever49 is operatively connected to the fast idle cam 64 by a pivotallyconnected rod 66. As the valve 20 is closed the lever 46} urges cam 64to rotate in the direction of the illustrated arrow about the pivot pin68 which is stationarily se cured to the carburetor. The cam 64 engagesthe throttle valve control lever 70 to increase engine speed as thechoke valve is moved toward the closed position. It is understood thatthe lever 70 is non-rotatably secured to the usual carburetor throttlevalve such as illustrated in FIG. 241 on page 312 of James V. Frostsbook Pre-service Course in Automotive Mechanics, John Wiley & Sons, NewYork, 1943.

During engine warmup the valve 2t) tends to open as the engine speedincreases through the action of pressure unit 26. The fast idle speed isdetermined by the combined forces of calibrated spring 36, spring motor24 and spring 28 as balanced by the force of the engine speed indicatingpressure flexing of the diaphragm 34 plus the slight force from thevalve 29 due to air passing thereby. The fast idle speed may be variedby adjusting any of the above listed items or any of the linking rodswith the fast idle speed being governed in part by true engine speed. Asthe engine warms up, the motor 24 begins to open the choke valve toprogressively decrease the fast idle speed in proportion to increasingengine temperature. that the maximum fast idle speed is alwaysdetermined by engine speed responsive unit 26.

It is understood that suitable modifications may be made in thestructure as disclosed, provided such modifications come within thespirit and scope or" the appended claims. Having now therefore fullyillustrated and described by invention, what I claim to be new anddesire to protect by Letters Patent is:

1. In an outboard motor having an internal combustion engine with acarburetor having an air intake passageway, a choke valve mounted in thepassageway and being rotatable between open and closed positions, ongine cooling means providing liquid coolant and operatively connected tothe engine for developing coolant pressures related to engine speed,pressure responsive linkage means communicatively associated with thecooling means and operatively connected to the valve for rotating ittoward the open position as the coolant pressure increases, and meansyieldably urging the valve toward the closed position.

2. In an outboard motor having an internal combustion engine with acarburetor having an air intake passageway, a choke valve mounted in thepassageway and being rotatable between open and closed positions, enginecooling means providing liquid coolant and operatively as- Note 4sociated with the engine for developing pressures proportional to enginespeed, a pressure flexible diaphragm communicatively associated with thecooling means for being flexed in a first direction, resilient meansopera tively connected to the diaphragm for yieldably urging thediaphragm to flex oppositely to the first direction, and the diaphragmbeing operatively connected to the valve for rotating same toward theopen position as the pressure increases in proportion to engine speed.

3. In an outboard motor having an engine with a carburetor with an airintake passageway, a choke valve mounted in the passageway and rotatablebetween open and closed positions by a choke valve lever non-rotatablyassociated therewith, spring means on the engine and being operativelyconnected to the valve for yieldably urging same toward the closedposition, engine cooling means operatively associated with the enginefor developing coolant pressures proportional to engine speed, travellimited pressure responsive means communicatively associated with thecooling means and operatively engaged with the valve lever foroverriding the yiei-dabic spring means to limitedly rotate the valvetoward the open position in proportion to the coolant pressures andbeing disengageable from the valve lever when the valve is moved towardthe open position irrespective of coolant pressures.

4. In an automatic choke for an outboard motor internal combustionengine, a choke valve having control linkage and being operable betweenopen and closed positions, an engine temperature responsive motoroperatively associated with the linkage for opening and closing thevalve as engine temperature respectively increases and decreases, anengine cooling system operatively associated with the engine fordeveloping coolant pressures related to engine speed, a travel-limitedpressure responsive means communicatively connected to said coolantmeans and being operatively engaged with the choke valve linkage atleast when the motor is somewhat urging the valve toward the closedposition, the pressure responsive means being responsive to increasingcoolant prcssures to override the motor urging for opening the valve inproportion to engine speed, and the pressure means being operativelydisengageable from the linkage as the motor urges the valve toward theopen position.

5. In an outboard motor having an internal combustion engine, acombustion air control valve means communicatively associated with theengine and having open and closed positions, a spring connected to thevalve means for yieldably urging it closed, an engine temperatureresponsive motor operatively associated with the valve means to opensame in proportion to engine temperatures, an engine cooling systemoperatively associated with the engine for developing coolant pressuresproportional to engine speed, a pressure responsive diaphragm unithaving a pressure responsive diaphragm and being communicativelyassociated with the cooling system for flexing the pressure responsivediaphragm in one direction, stop means in the unit for limiting thediaphragm flexing in the one direction, resilient means in the unitengaging the diaphragm for yieldably urging it opposite to the onedirection, and the unit being operatively engaged with the valve meansfor opening same only when the diaphragm is flexed to provide a valvemeans opening exceeding or equaling a valve means opening being providedby the temperature motor.

6. In an outboard motor internal combustion engine having combustion airintake means with a choke valve operable between open and closedpositions, the valve being offset mounted on a shaft journaled throughthe intake means such that air drawn in through the means will partiallyopen the valve, lever means on the shaft for operating the valve,exhaust means on the engine, a thermostatic spring motor operativelyconnected to the lever means and being in fluid communication withoutside the engine through the exhaust means for receiving air heatedthereby and being responsive to the heated air for opening the valve inproportion to the heated air temperature, engine cooling means providingwater under pressure to the engine in proportion to the engine speed, apressure responsive unit communicatively associated with the coolingmeans and having a diaphragm exposed and being responsive to the coolingmeans pressures for flexing in one direction, diaphragm flexing limitingand disengageable means connecting the diaphragm to the lever means forcommunicating diaphragm pressure flexing to the lever means to partiallyOpen the valve proportionately to engine speed, and the connecting meansdisengaging and freeing the lever means from the pressure unit when thespring motor has operated the valve toward the open position more thansaid partial opening.

7. In a fast idle for an internal combustion engine in an outboardmotor, a choke valve, a throttle control, fast idle means connecting thevalve to the control for increasing the engine speed up to apredetermined rate as the valve is closed, an engine cooling systemdrawing water from outside the engine and providing same to the engineunder pressures related to engine speed, a pressure responsive devicecommunicatively associated with the cooling system and being operativelyengaged with the choke valve for opening same as the pressures increase,means yieldably urging the Valve to be closed, and means for varying themaximum fast idle engine speed as a function of the actual engine speed.

8. Apparatus as in the claim 7 wherein the yieldable urging meansincludes a thermostatic spring motor for yieldably urging the valve tovary between being open and closed as a function of engine temperaturewhereby at a predetermined engine temperature the valve is sulficientlyoperated toward the open position whereby the pressure device isoperatively disengaged from the valve.

9. In an outboard motor having an internal combustion engine with acarburetor having an air intake passageway, a choke valve mounted in thepassageway and being rotatable between open and closed positions, enginecooling means providing liquid coolant and operatively connected to theengine for developing coolant pressures related to engine speed,pressure responsive linkage means communicatively associated with thecooling means and operatively connected to the valve for proportionatelyrotating it toward the open position in accordance with increases ofpressure and means yieldably urging the valve toward the closedposition.

10. In an outboard motor having an internal combustion engine with acarburetor having an air intake passageway, a choke valve mounted in thepassageway and being rotatable between open and closed positions, enginecooling means operatively associated with the engine for developingpressures proportional to engine speed, a pressure flexible diaphragmcommunicatively associated with the cooling means for being flexed in afirst direction, resilient means operatively connected to the diaphragmfor yieldably urging the diaphragm to flex oppositely to the firstdirection, said diaphragm being operatively connected to the valve forproportionately rotating same toward the open position as the pressureincreases in proportion to engine speed.

11. In an internal combustion engine; an air inlet to an air-fuel mixingdevice; a moveable choke valve mechanism positioned in said air inlet;liquid engine cooling means including means operatively connected to anengine for developing liquid coolant circulation pressures proportionalto engine speed; means biasing said choke valve to a position tending toreduce the flow of air through said air inlet and means responsive tosaid proportional pressure and connected to said choke valve mechanismin a manner to overcome said biasing means so as to tend to move saidchoke valve mechanism proportionately toward a position tending toincrease the flow of air through said inlet.

References Cited in the file of this patent UNITED STATES PATENTS2,225,636 Joeck Dec. 24, 1940 2,245,672 Hunt June 17, 1941 2,297,355Hughes Sept' 29, 1942 2,548,334 Armstrong Apr. 10, 1951

